Performance of HRP-2 based rapid diagnostic test for malaria and its variation with age in an area of intense malaria transmission in southern tanzania
Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom; Ifakara Health Institute, Dar es Salaam, Tanzania; Barcelona Centre for International Health Research, Barcelona, Spain; Swiss Tropical and Public Health Institute, P.O. Box 4002, Basel, Switzerland; University of Basel, 4002 Basel, Switzerland
Background. The use of malaria rapid diagnostic tests (RDTs) has been widely advocated to improve Plasmodium falciparum diagnosis, especially in settings where quality microscopy is not available. RDTs based on the detection of histidine-rich protein 2 (HRP-2) can remain positive for several weeks after an infection is cured, due to the persistence of HRP-2 antigens. As a result, test specificity may vary between age groups with different prevalence of P. falciparum infection. Methods. A community-based cross-sectional survey, carried out in southern Tanzania in July and August 2004, evaluated the performance of the Paracheck Pf in comparison with microscopy (number of P. falciparum parasites/200 leucocytes). A sample of 598 individuals living in an area of intense malaria transmission had demographic data collected before an RDT was performed. HRP-2 test sensitivity, specificity, positive and negative predictive values were calculated and compared between distinct age groups, using microscopy as "gold standard". Results. The overall malaria prevalence was 34.3% according to microscopy and 57.2% according to the HRP-2 test. The HRP-2 test had a sensitivity of 96.1%, a specificity of 63.1%, a positive predictive value of 57.6% and a negative predictive value of 96.9%. The test sensitivity was higher (ranging from 98% to 100%) amongst people less than 25 years of age, but decreased to 81.3% in older adults. The HRP-2 test specificity varied between age groups, ranging from 25% among children of five to nine years of age, to 73% among adults aged 25 or more. The test positive predictive value increased with malaria prevalence, while the negative predictive value was consistently high across age groups. Conclusions. These results suggest that the performance of HRP-2 tests in areas of intense malaria transmission varies by age and the prevalence of P. falciparum infection. The particularly low specificity among children will lead to the over-estimation of malaria infection prevalence in this group. © 2010 Laurent et al; licensee BioMed Central Ltd.
histidine rich protein 2; protozoal protein; unclassified drug; HRP 2 antigen, Plasmodium falciparum; HRP-2 antigen, Plasmodium falciparum; parasite antigen; protozoal protein; adolescent; adult; age distribution; aged; article; child; controlled study; demography; diagnostic test; female; gold standard; human; major clinical study; malaria falciparum; male; microscopy; parasite transmission; Plasmodium falciparum; prevalence; sensitivity and specificity; Tanzania; age; comparative study; cross-sectional study; diagnostic test; evaluation; infant; isolation and purification; malaria falciparum; methodology; newborn; parasitology; predictive value; preschool child; Adolescent; Adult; Age Factors; Antigens, Protozoan; Child; Child, Preschool; Cross-Sectional Studies; Diagnostic Tests, Routine; Female; Humans; Infant; Infant, Newborn; Malaria, Falciparum; Male; Microscopy; Parasitology; Plasmodium falciparum; Predictive Value of Tests; Protozoan Proteins; Sensitivity and Specificity; Tanzania; Young Adult